Method and apparatus to determine tube current modulation profile for radiographic imaging
First Claim
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1. A method of tube current modulation for radiographic data acquisition, the method comprising the steps of:
- identifying a plurality of modulation points on a waveform indicative of at least one of subject size and subject shape;
determining a modulation factor at the plurality of modulation points; and
generating a modulation tube current waveform that substantially approximates the waveform indicative of at least one of subject size and subject shape based on a modulation factor at the plurality of modulation points.
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Abstract
A method and apparatus is disclosed to acquire scout scan data of a subject and analyzed to determine a peak-to-peak modulation amplitude of a normalized waveform indicative of subject size and shape. The scout scan data provides a representation of patient size and shape that is associated with an ideal tube current modulation waveform or profile. The ideal tube current modulation profile may then be sampled or approximated at various points to determine a tube current modulation profile for implementation to acquire CT data with reduced dose but without sacrificing image quality.
67 Citations
21 Claims
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1. A method of tube current modulation for radiographic data acquisition, the method comprising the steps of:
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identifying a plurality of modulation points on a waveform indicative of at least one of subject size and subject shape; determining a modulation factor at the plurality of modulation points; and generating a modulation tube current waveform that substantially approximates the waveform indicative of at least one of subject size and subject shape based on a modulation factor at the plurality of modulation points. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A CT system comprising:
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a gantry having an opening to receive a subject to be scanned; a high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the subject; a scintillator array having a plurality of scintillator cells, wherein each cell is configured to detect high frequency electromagnetic energy passing through the subject; a photodiode array optically coupled to the scintillator array and comprising a plurality of photodiodes configured to detect light output from a corresponding scintillator cell; a data acquisition system (DAS) connected to the photodiode my and configured to receive photodiode outputs; an image reconstructor connected to the DAS and configured to reconstruct an image of the subject from the photodiode outputs received by the DAS; and a computer programmed to; determine an ideal tube current modulation waveform to control projection of high frequency electromagnetic energy by the high frequency electromagnetic energy projection source for CT data acquisition from the subject; evaluate the ideal tube current modulation waveform at a plurality of magnitudes; generate at least one polynomial expression fit to values evaluated at the plurality of magnitudes; and determine an approximate tube current modulation waveform from the at least one polynomial expression. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A computer readable storage medium having a computer program stored thereon and representing a set of instructions that when executed by a computer causes a computer to:
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command a radiographic data acquisition system to carry out a scout scan to acquire pre-scan data indicative of subject size and subject shape; determine a first tube current modulation waveform ideal for the subject size and the subject shape front the pre-scan data; evaluate a portion of the first tube current modulation waveform corresponding to ninety degrees of gantry rotation; and determine a second tube current modulation waveform that approximates the first tube current modulation waveform from a polynomial fit of the evaluated portion of the first modulation waveform. - View Dependent Claims (19, 20)
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21. A CT system comprising:
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a gantry having an opening to receive a subject to be scanned; a high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the subject; a scintillator array having a plurality of scintillator cells, wherein each cell is configured to detect high frequency electromagnetic energy passing through the subject; a photodiode ray optically coupled to the scintillator array and comprising a plurality of photodiodes configured to detect light output from a corresponding scintillator cell; a data acquisition system (DAS) connected to the photodiode array and configured to receive photodiode outputs; an image reconstructor connected to the DAS and configured to reconstruct an image of the subject from the photodiode outputs received by the DAS; and a computer programmed to; determine an ideal tube current modulation waveform from a scout scan to control projection of high frequency electromagnetic energy by the high frequency electromagnetic energy projection source for CT data acquisition from the subject wherein the ideal tube current modulation waveform is a function of oval ratio and minimum subject diameter during a one-quarter gantry rotation cycle; determine a size and a shape of the subject from the scout scan; determine the size and the shape from data acquired in one-quarter of gantry rotation; evaluate the ideal tube current modulation waveform at a plurality of magnitudes; and determine an approximate tube current modulation waveform from values at the plurality of magnitudes.
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Specification